We study the process $e^{+}{e}^{-}\to W^{+}{W}^{-}$ with the aim of estimating the prospects for observing heavy neutrino contributions at future $e^{+}{e}^{-}$-colliders. In this work, we consider two implementations of heavy-light neutrino mixing: a linearized mixing approximation applied in popular models and an exact unitary mixing scheme. We conclude that the approximate realization leads to physically incorrect results for this process, while exact unitary mixing provides some signatures that can be experimentally checked.

Proton-proton fusion is the fundamental weak reaction initiating stellar energy production, and a first-principles determination of its matrix element remains a long-standing goal of nuclear theory. We present a lattice QCD calculation of the proton-proton fusion matrix element at a pion mass of $m_{\pi }\approx 432\mathrm{MeV}$. For this process, we implement Lellouch–Lüscher finite-volume corrections within a systematic $2+\mathcal{J}\to 2$ framework, explicitly accounting for two-nucleon rescattering effects, to relate finite-volume matrix elements to their infinite-volume counterparts. Excited-state contamination is suppressed using bilocal nucleon-nucleon interpolating operators, together with a variational analysis employing operators with the three lowest momenta. This strategy enables the determination of the two-nucleon energy spectrum and scattering parameters via Lüscher’s finite-volume formalism. Prior to including rescattering effects in the Lellouch–Lüscher factor, we obtain a reference value $⟨d|\mathcal{J}|pp⟩/g_A=0.984(10)$, where $g_A$ is the nucleon axial charge. The deviation from unity indicates a small but nonvanishing contribution from two-body currents. Our analysis shows that rescattering effects entering the Lellouch–Lüscher factors can substantially modify the two-body contribution, while large uncertainties in the two-nucleon scattering parameters propagate strongly into the finite-volume corrections. As a result, a precise determination of the two-body low-energy constant $L_{1,A}$ remains highly challenging with current lattice inputs. Despite the large uncertainty, the resulting value $L_{1,A}=6.0(7.1){\mathrm{fm}}^3$ is compatible, at the level of naturalness and order of magnitude, with existing phenomenological extractions from experimental data. This work demonstrates both the feasibility and the intrinsic challenges of ab initio lattice QCD calculations of weak two-nucleon reactions, and establishes a foundation for future studies at or near the physical pion mass.

We study the signatures of the chiral magnetic effect (CME) in $SU(2)$ gauge theory with $N_f=2$ flavors of dynamical fermions at finite temperature $T$, quark chemical potential $\mu$ and a weak external magnetic field $eB$. We consider both the correlator of the axial density and the vector current, which gives direct access to the out-of-equilibrium CME, and the correlator of two vector currents, which probes the CME indirectly via the enhancement of the longitudinal electric conductivity (negative magnetoresistance, NMR). We find that the CME response extracted from the vector-axial correlator exhibits a rather weak dependence on temperature and density in the quark-gluon plasma regime, and is very close to the universal value for free massless quarks. The CME appears to be mildly suppressed at low temperatures in the hadronic phase. In contrast, the NMR behaves in a qualitatively different way across the phase diagram, and is strongly suppressed at either large densities or temperatures. The magnitude of the NMR response appears to be considerably smaller than the prediction based on the lowest Landau level calculation for free quarks. Our findings suggest that for relatively small magnetic field strengths $eB\lesssim m_{\pi }^2$ the relation between the CME and NMR might not be as direct as expected. We also do not find statistically significant indications for an enhancement of the CME or NMR strength in the vicinity of the crossover or second-order phase transition lines in the $(\mu ,T)$ phase diagram.

The resonating group method (RGM) is widely used to investigate baryon-baryon interactions at the quark level, typically under the assumption that the two baryons involved share an identical harmonic oscillator frequency. In reality, however, when a specific interaction Hamiltonian is given, different baryons should have unequal oscillator frequencies due to distinct interaction potentials induced by their different quantum numbers. In this work, we develop a new quark-level RGM formalism for baryon-baryon systems with unequal oscillator frequencies, with the aim of providing a unified and consistent framework for describing both single-baryon properties and baryon-baryon interactions. We present the formalism for solving bound-state and scattering problems, with particular emphasis on constructing the wave functions of two-baryon systems with unequal oscillator frequencies. The proposed formalism is then applied to the $N\mathrm{\Delta }$ system within a chiral SU(3) quark model, where the quark-quark interaction includes, in addition to the one-gluon exchange and a phenomenological confinement potential, the nonet scalar and pseudoscalar meson exchanges arising from the spontaneous breaking of chiral SU(3) symmetry. The distinctive features of the newly developed formalism are demonstrated by comparing the results from the new formulation with those from traditional calculations.

Potential experimental signatures of gluon generalized transverse momentum-dependent distributions (GTMDs) are proposed via exclusive heavy (axial-)vector meson production in lepton-proton collisions. Within the framework of collinear twist-3 factorization, we show that specific azimuthal-angle-dependent observables can provide sensitivity to the gluon GTMDs $F_{1,4}^g$ and $G_{1,1}^g$, which are related to partonic orbital angular momentum and spin-orbit correlations, respectively. These functions represent a unique sector of nucleon structure with no counterparts in the generalized parton distribution or transverse-momentum-dependent frameworks. We show that interference between different virtual-photon polarizations leads to distinct azimuthal modulations, including the polarization-independent $\cos 2\varphi$ and polarization-dependent $\sin 2\varphi$ terms, with $\varphi$ defined as the angle between the lepton scattering plane and the hadron production plane. These observables provide signatures of the elusive gluon GTMDs $F_{1,4}^g$ and $G_{1,1}^g$, opening a new channel to access the spin structure of the nucleon at the future Electron-Ion Collider.

We compute the tree-level and one-loop matching relations for leading power gluon transverse momentum dependent parton distribution functions. At tree level, working within the spinor formalism, we focus on twist-2 and twist-3 contributions, deriving the series of mass corrections for both T-even and T-odd distributions within the considered twist accuracy. At one-loop accuracy, we extend the parton-in-parton framework to include contributions beyond the leading term in the small-$b$ expansion. Applying this methodology to the gluon sector, we obtain for the first time the Wandzura-Wilczek approximation for the gluon worm-gear T distribution. Furthermore, we develop a method to include the twist-2 contribution to the mass corrections in one-loop results and provide a closed-form expression for the mass series suitable for numerical implementations.

A long-standing problem in electroweak phase transition studies is the spurious gauge dependence of bubble nucleation rate calculations, which introduces large systematic uncertainties in predictions of gravitational waves and related cosmological phenomena. We address this issue by presenting a systematic study of gauge-invariant bubble nucleation within a phenomenologically realistic effective field theory framework. Using the three-dimensional thermal effective field theory formalism with a consistent power-counting scheme, we rigorously establish the gauge invariance of the physical nucleation rate up to two-loop order. This proof eliminates the gauge-parameter dependence of key phase transition parameters, providing a robust theoretical foundation for precise calculations of gravitational waves, electroweak baryogenesis, and primordial magnetogenesis.

We develop the (super)twistor approach to D0-brane, which is the massive type IIA superparticle in ten-dimensional spacetime. The basic variables are hexadecuplet of constrained $OSp(32|1)$ supertwistors similar but not identical to the ones which have been used for the description of 11D massless superparticle, also known as M0-brane. We show how the constrained supertwistor formulation is related to the spinor moving frame approach to D0-brane. We perform the quantization of the model by two different methods and discuss the relation of the results with the quantization of the spinor moving frame formulation of D0-branes. The quantum state spectrum describes the massive counterpart of the linearized type IIA supergravity.

The origin of large scale magnetic fields in the Universe is widely thought to be from early Universe processes, like inflation or phase transitions. These magnetic fields evolve via magnetohydrodynamic processes until the epoch of recombination. When structures begin to form in the later Universe, the conservation of magnetic flux amplifies the magnetic fields via the adiabatic collapse of gravitationally bound gas clouds hosting the magnetic fields and moves them to smaller scales. In this work, we have semianalytically studied this forward cascade effect, considering simple models of gravitational collapse of structures. We find that this simple model is able to reproduce the general qualitative features of the evolution of the magnetic field spectrum as seen from magnetized cosmological simulations.

Measurement of the optical depth to reionization (${\tau }_{\mathrm{reio}}$) is largely driven by the large-scale EE polarization data of cosmic microwave background (CMB) ($\ell <30$). Removing the low-$\ell$ EE data potentially alleviates various cosmological tensions. In this work, we study the effect of the low-$\ell$ EE polarization measurements on the Chevallier-Polarski-Linder (CPL), Jassal-Bagla-Padmanabhan (JBP), and Barboza-Alcaniz (BA) dark energy parametrizations using CMB data from Planck and Atacama Cosmology Telescope Data Release 6, combined with a Dark Energy Spectroscopic Instrument baryon acoustic oscillation and PantheonPlus compilation of type Ia supernovae. We find that excluding low-$\ell$ EE data shifts ${\tau }_{\mathrm{reio}}$ and $A_s$ to higher values through the unbroken $A_s-{\tau }_{\mathrm{reio}}$ degeneracy with a $\sim (1.4–1.8)\sigma$ shift in $A_s$ for $\mathrm{\Lambda }\mathrm{CDM}$ (cold dark matter) and JBP, and a milder $\sim 1\sigma$ shift for CPL and BA. The equation of state (EOS) for all three parametrizations moves toward the quintessence regime [$w(z)>-1$] upon exclusion of low-$\ell$ EE data, driven primarily by the strengthening of the $w_a-A_s$ and the $w_a-{\tau }_{\mathrm{reio}}$ correlations, with a small effect from the correlations of $w_0$ with $A_s$ and ${\tau }_{\mathrm{reio}}$. The most prominent effect occurs in JBP, where the EOS lies entirely within the quintessence regime at $1\sigma$ when excluding low-$\ell$ EE data. Model comparison through the Akaike information criterion shows positive evidence in favor of CPL and BA and weak evidence in favor of JBP, robust to the inclusion of low-$\ell$ EE data and CMB data used. The deviance information criterion model comparison shows strong evidence in favor of CPL and BA when low-$\ell$ EE data are included, and positive evidence when they are excluded. For JBP, we get positive (weak) evidence when including (excluding) low-$\ell$ EE data over $\mathrm{\Lambda }\mathrm{CDM}$.

As discussed in a number of recent papers, cosmological stasis is a phenomenon wherein the abundances of multiple cosmological energy components with different equations of state remain constant for an extended period despite the expansion of the universe. One of the most intriguing aspects of the stasis phenomenon is that it can give rise to cosmological epochs in which the effective equation-of-state parameter $⟨w⟩$ for the universe is constant but differs from the canonical values associated with matter, radiation, vacuum energy, etc. Indeed, during such a stasis epoch, the spatial average of the energy density of the universe evolves in precisely the same manner as it would have evolved if the universe were instead dominated by a perfect fluid with an equation-of-state parameter equal to $⟨w⟩$. However, as we shall demonstrate, this equivalence is broken at the level of the perturbations of the energy density. To illustrate this point, we consider a stasis epoch involving matter and radiation and demonstrate that within this stasis background the density perturbations associated with a spectator matter component with exceedingly small energy density exhibit a power-law growth that persists across the entire duration of the stasis epoch. This growth can potentially lead to significant enhancements of structure at small scales. Such enhancements are not only interesting in their own right but may also provide a way of observationally distinguishing between a stasis epoch and an epoch of perfect-fluid domination—even if the universe has the same equation of state in both cases.

The temporal dependence of the astrophysical stochastic gravitational-wave (GW) background (SGWB) in the hecto-hertz band brings a unique avenue to identify multimessenger signals to these sources by using coincident detection in both GW and multiband electromagnetic (EM) signals. We developed a new analysis pipeline, multimessenger cross-correlation (${\mathrm{MC}}^2$) that can search for EM counterparts to the SGWB signal originating from both modeled and unmodeled sources by harnessing the nearly full-sky gamma-ray sky map. We provide an observation strategy that can be followed by current and future missions to discover EM counterparts to the weak GW signal hidden in the SGWB. We demonstrate the ability of this technique to drastically reduce the false alarm rates when involving EM multiband analysis. This formalism aims toward advancing the multimessenger observation frontier and improving our understanding of the population of bright SGWB sources present in the high-redshift universe and can also be applied to other messengers such as neutrinos in the future.

We present a geant4 Monte Carlo simulation of cosmic-ray (CR) hadronic interactions in a spherical molecular cloud ($\sim 5400M_{\odot }$, 13 concentric shells, $r^{-1.2}$ density profile) using six primary CR species, protons, alpha particles, carbon, oxygen, silicon, and iron, drawn from galprop-helmod local interstellar spectra over $1\mathrm{GeV}{\mathrm{nuc}}^{-1}$ to $1\mathrm{PeV}{\mathrm{nuc}}^{-1}$, the hadronic interaction regime in which pion production and nuclear spallation dominate the secondary particle output. We compute, for the first time within this framework, radial energy deposition profiles, per-layer secondary production rates, and the differential physical flux of all emerging stable secondaries for the full nuclear CR composition. Energy deposition scales as $Z^2$, with the secondary cascade dominating $\ge 92\%$ of the deposited energy in the dense core for all species. Alpha particles produce the highest integrated gamma-ray flux ($0.125{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$ above 100 MeV), followed by protons ($6.71\times {10}^{-2}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$); together, they account for $\approx 96\%$ of the total emerging gamma-ray and neutrino fluxes. A robust composition-diagnostic signature emerges in the neutrino sector: the ${\nu }_e/{\overline{\nu }}_e$ ratio above 100 MeV decreases from $\approx 6.4$ for protons, driven by the ${\pi }^{+}/{\pi }^{-}\approx 8–11$ charge asymmetry, to $\approx 2.8$ for $N=Z$ nuclei (C, O, Si), directly encoding the isospin content of the primary CR beam in an observable flux ratio. Secondary nuclear clusters ($d$, $t$, ${}^3\mathrm{He}$, $\alpha$, and heavier ions up to $Z=26$) emerge exclusively for nuclei heavier than protons, contributing at the $\approx 32\%$ level of the secondary proton flux for light clusters, while heavy-ion fragments remain 1 to 2 orders of magnitude below the secondary proton channel.

We perform a comprehensive analysis of cosmic-ray propagation using the time-dependent AMS-02 flux measurements covering a full solar cycle, with particular emphasis on the role of solar modulation. We fit two representative Galactic propagation scenarios, convection- and reacceleration-dominated models, in combination with three solar modulation prescriptions: the standard force-field approximation, an extended force-field model with a rigidity break, and the heliospheric propagation code helmod. The inclusion of time-resolved antiproton data provides a unique probe of charge-sign-dependent modulation effects and low-energy systematics. We find that the force-field approximation can describe positively charged nuclei reasonably well outside the solar maximum in convection-dominated models, but fails during periods of high solar activity and for antiprotons at all times. In reacceleration scenarios, strong degeneracies between solar modulation and low-energy propagation lead to unphysical results when simple modulation models are employed. Across all models, we identify systematic uncertainties of order 10%–15% in the reconstructed local interstellar spectra and propagation parameters, driven by limitations in current solar modulation modeling. Compared to the percent level error of current measurements, these uncertainties significantly limit the precision of cosmic-ray studies. Future time-dependent measurements spanning a full 22-year solar cycle will be crucial to reduce these uncertainties.

We comment on the recent analysis reported in [Phys. Rev. D 113, 016024 (2026)], where quantum coherence, entanglement, steering, and non-Markovian dynamics were investigated in the process $e^{+}{e}^{-}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$. While the mathematical framework employed in that work may be formally well defined, we argue that several physical assumptions underlying its interpretation require further clarification. In particular, the treatment of the produced hyperon-antihyperon pair as an open bipartite system evolving under correlated quantum channels does not appear to follow naturally from the physical properties of the process. Moreover, the operational meaning of quantum steering and non-Markovianity in this relativistic unstable-particle system remains unclear due to the absence of controllable local measurements, engineered environments, and experimentally accessible dynamical maps. We emphasize that quantum-information-inspired observables can provide useful characterizations of spin correlations in high-energy reactions when their operational interpretation and physical assumptions are carefully specified. Our purpose is therefore not to question the mathematical consistency of the analyzed formalism, but rather to clarify the physical limitations associated with its interpretation in the $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ system.

Building on previous studies that demonstrated the applicability of a fluid-dynamic description of charm quarks in the quark-gluon plasma [Phys. Rev. D 106, 034021 (2022); Phys. Rev. D 108, 116011 (2023).], the present work extends the framework by computing the out-of-equilibrium contributions to the distribution function of charm hadrons. The analysis includes corrections arising from the initial out-of-equilibrium distribution of charm quarks after a free-streaming phase, as well as from the freeze-out surface within fluid dynamics. These results enable the exact computation of integrated yields and transverse-momentum distributions of charm hadrons for different values of the spatial diffusion coefficient, thereby providing the basis for a systematic determination of the charm transport coefficients. A preliminary comparison of our model with the available experimental data shows compatibility within uncertainties. In addition, the limits of applicability of the approach are identified by determining the transverse-momentum region in which charm hadrons are described by a well-defined, positive distribution function.

High-performance machine learning tools in particle physics rest on two complementary directions: encoding symmetries explicitly in the architecture, and implicitly learning the structure of the data through large-scale (pre)training. We compare the performance of the representative Lorentz Geometric Algebra Transformer and omnilearn models on three especially challenging tasks: reweighting-based unfolding, likelihood-ratio estimation, and weakly supervised anomaly detection. Across all benchmarks, both methods achieve comparable performance given the statistical precision of the finetuning datasets, suggesting that the significant efficiency gains from encoding known particle physics structures are largely method independent.

We use the Wentzel-Kramers-Brillouin approximation to uncover divergences and instances of noncommuting limits in a large class of holographic soft-wall models. We show that the infinite sum over single resonance contributions for a variety of observables involving the Chern-Simons term, such as the vector-vector-axial-vector (VVA) correlator or the hadronic light-by-light tensor, does not converge. These divergences can in some cases (such as the VVA correlator) be traced back to noncommuting limits and avoided by working directly in the five-dimensional setup with bulk-to-boundary propagators. However, the hadronic light-by-light scattering tensor also diverges in the five-dimensional formulation with corresponding Green functions, preventing a correct implementation of the Melnikov-Vainshtein short-distance constraint and even leading to an infinite contribution to the muon $g-2$. We also discuss modifications of the standard soft-wall model that are able to resolve this issue.

Current and future neutrinoless double-beta decay ($0\nu \beta \beta$) searches are usually characterized by half-life limits or projected sensitivities. For operator-level interpretation, however, the relevant question is not only the strength of the limit, but also the stability of the inferred constraints on low-energy lepton number violation (LNV) coefficients under changes of isotope and the nuclear matrix element (NME) method. Using $\nu \mathtt{DoBe}$, we convert half-life limits or projected sensitivities into limits on low-energy LNV coefficients for several choices of isotope, operator class, and NME method. We then compare the resulting limits across isotopes and NME methods. We quantify the stability by the spread of coefficient limits in nonobservation scenarios and, for single-operator postdiscovery benchmarks, by the spread of isotope-to-isotope half-life ratios. For the operator examples considered in this paper, the light-Majorana exchange mechanism gives the most stable interpretation. The selected dimension-six operators remain reasonably robust, while the short-range dimension-nine examples show a stronger dependence on isotope and NME method choices. The same hierarchy appears in postdiscovery benchmarks based on isotope-to-isotope half-life ratios: the reliability of such tests depends on whether the predicted half-life pattern remains stable across NME methods. A multi-isotope $0\nu \beta \beta$ program, therefore, provides information beyond half-life reach by testing the stability of the operator interpretation. This spread-based analysis provides a practical way to identify which low-energy operator scenarios are suitable for isotope ratio tests after a possible discovery, and which require more care before being connected to ultraviolet models of lepton number violation.